Deprivation and NHS General Ophthalmic Service sight testing activity in England in 2022-2023.

PURPOSE: Socioeconomic deprivation is associated with an increased incidence of sight-loss. To inform potential developments in eyecare, General Ophthalmic Service (GOS) sight-testing activity was explored in relation to deprivation for GOS contractors submitting National Health Service (NHS) claims in England. METHODS: Data on NHS sight-test claims for the financial year 2022-2023 were sought from NHS England (NHSE), including number of sight-tests by GOS contractors, their unique Organisation Data Service codes and postcodes and age-bands of patients accessing sight-testing. Deprivation scores were assigned to contractor practices using the Index of Multiple Deprivation (IMD) and the average number of sight-tests for all contractors within each IMD decile calculated, allowing rate of sight-testing per 1000 population per decile of deprivation to be estimated using Office of National Statistics (ONS) Lower Layer Super Output Area mid-year population estimates. Inequality was examined using the Odds Ratio (OR) and slope and relative index of inequality measures (SSI and RII). RESULTS: Overall, 12.94 million NHS sight-tests were provided by 5622 GOS contractors in England in 2022-2023. Most affluent decile GOS contractors undertook an average ~2200 NHS sight-tests, while in the most deprived decile, average NHS sight-tests per contractor was ~1100. Rate of sight-testing per 1000 population in the most deprived decile was one quarter of that in the most affluent, with an OR of 5.29 (95% CI 5.27-5.30), indicating those in the most affluent areas were ~five times more likely to access NHS sight-tests. Overall, SII and RII were 333.5 (95% CI 333.52-333.53) and 6.4 (95% CI 6.39-6.40), respectively, findings reflective of substantial inequality in uptake. CONCLUSION: There remains substantial unwarranted variation in uptake of NHS sight-testing, with those in more affluent areas accessing sight-testing substantially more than those in more deprived areas. Strategies are required to facilitate primary care optometry to provide more equitable access to eyecare.

Driving and exceptional cases: Supporting relicensing evaluation in patients whose visual fields fail to meet standards.

PURPOSE: The UK Driver and Vehicle Licensing Agency's (DVLA) visual field criteria mean that homonymous defects close to fixation are not usually acceptable for driving. Here, we illustrate cases where patients with field defects failing to meet standards had their licences revoked but subsequently were permitted to drive again through exceptional case provisions. METHODS: Clinical assessment of two patients with homonymous loss: a 62-year-old man (PWT) with a dense left upper homonymous quadrantanopia secondary to a right occipital lobe stroke and a 48-year-old woman (JC), only aware of right upper homonymous quadrantanopia following routine primary care assessment and subsequently attributed to left middle cerebral artery stroke from perinatal intracranial haemorrhage. RESULTS: PWT's Esterman test showed a significant central defect failing to meet the standard. His subsequent ophthalmic examination was otherwise unremarkable with excellent visual functions. Clinical evidence was provided supporting his relicensing application, and in time, a practical DVLA driving assessment indicated adaptation had been successful, and his licence was restored. JC's defect also failed to meet the standard, and her licence was revoked. Her ophthalmic examination was otherwise unremarkable, and her condition was attributed to a nonprogressive, isolated perinatal event. The DVLA accepted supporting clinical evidence; her subsequent practical driving assessment demonstrated successful adaptation and her licence was also restored. CONCLUSIONS: Conventional visual field tests are not necessarily predictive of real-world driving performance, with drivers' adaptive strategies not being accommodated. In the UK, individuals with visual field loss failing to meet the standard may be eligible for relicensing as exceptional cases if specific criteria can be met. For exceptional cases potentially licensable under these criteria, the DVLA requires clinician support and a satisfactory practical driving assessment. Similar provisions exist internationally. Clinicians need to be aware of the role they may play in such scenarios.

Scope of practice of optometrists working in the UK Hospital Eye Service: Second national survey.

PURPOSE: As the landscape in ophthalmology and related commissioning continues to change, there is a pressing need to re-evaluate the current scope of practice of hospital optometrists working within secondary care in the UK. We aim to establish if the skills or services delivered by optometrists have changed to meet varying demands, and to better understand what changes in practice may have arisen as a result of COVID-19. METHOD: A survey developed from that used in 2015 was disseminated to 129 optometry Hospital Eye Service (HES) leads in September 2020, including questions on department workforce; core services; extended roles; procedures undertaken within extended roles; level of autonomy; arrangements for prescribing; training and accreditation, and service changes in response to COVID-19. RESULTS: Ninety responses were received (70% response rate) from within England (76%), Scotland (22%) and Northern Ireland (2%). Whole time equivalents within units ranged from 0.4-79.2 (median of 2.5). In comparison to the 2015 survey, there was an increase in the proportion of units delivering extended roles, with glaucoma (88%) remaining the most common extended role, and new areas of practice in uveitis (21%) and vitreoretinal (13%) services. There was increased use of independent prescribing (67%) in comparison to 18% in 2015 and there was an increase in optometrists delivering laser interventions. In response to COVID-19, optometrists were increasingly delivering telephone consultations and there were new collaborations between primary and secondary care. CONCLUSIONS: Optometrists' scope of practice continues to develop in the HES with an increased variety of roles and an apparent increase in the number of units employing optometrists, often working in roles historically performed by medical practitioners. Such changes appear necessary in recovery and transformation within ophthalmology, alongside wider optometry changes arising at the interface of primary and secondary care.

Evaluation of training, patient and practitioner perspectives on community-based monitoring of patients with stable age-related macular degeneration compared to hospital-based care: The FENETRE study report no. 1.

PURPOSE: Describe the development, delivery, acceptability and evaluation of a modular training programme for community-based, non-medical practitioners monitoring patients with quiescent neovascular age related macular degeneration (QnAMD). Also, report on a qualitative process evaluation conducted during the pilot phase of a randomised control trial (the FENETRE Study) exploring patient and practitioner acceptability of community-based QnAMD care relative to hospital-based care. METHODS: Learning outcomes from The College of Optometrists' Medical Retina higher qualifications and the Royal College of Ophthalmologists' Common Clinical Competency Framework were used to develop a competency framework for QnAMD care. Training was delivered online, comprising six asynchronous lectures followed by two synchronous case-based discussion webinars, with an accredited assessment of 24 case vignettes. An anonymous evaluation survey was conducted with the first two FENETRE cohorts (n = 38). Separately, we undertook a qualitative process evaluation, sampling purposively in four hospitals and five community-based practices, interviewing nine patients and eight practitioners. RESULTS: Survey responses (n = 26) showed community optometrists were very satisfied (n = 12; 46%) or satisfied (n = 14; 54%) with the training; feedback reflected by qualitative process evaluation data. Overall, optometrists also felt either confident (n = 15; 58%) or very confident (n = 8; 31%) in conducting AMD monitoring appointments following training, a finding also corroborated by interview data from optometrists participating in the initial pilot phase roll-out. Optometrists identified patient convenience and alleviating pressures in hospital care as the primary reasons for acceptability of community pathways. Data from patients entering community practices suggested they largely found this at least as safe and convenient as hospital care, although some patients randomised to hospital care perceived that as safer. CONCLUSION: This pilot study has shown the development and implementation of a collaborative community monitoring model is feasible, with satisfaction from community optometrists for training and accreditation, and broad acceptance for the pathway by both patients and practitioners.

Treatment decisions of UK hospital optometrists and ophthalmologists in patients with nAMD: a vignette study.

PURPOSE: A vignette study to examine treatment decisions made by UK hospital optometrists in patients with neovascular age-related macular degeneration (nAMD) and the effect of optometrists' experience on agreement. METHODS: Patients with nAMD attending Manchester Royal Eye Hospital, Manchester, UK were identified as potential candidates for the case series of vignettes. The cases were chosen to reflect a varied case-mix with respect to difficulty as well as ensuring good quality of the images. Each vignette included a history summary consisting of the number of previous injections given and visual acuity measurements at baseline, the previous visit, and the current visit. Images were compiled to show baseline fundus photographs and ocular coherence tomography (OCT) images with the current visit images on which the treatment decision was to be made along with the images from the previous visit. Hospital optometrists were recruited and asked to complete the series of vignettes, deciding if treatment was required at that visit and how confident they felt with that decision. Their responses were compared to the reference standard created by a consensus of consultant ophthalmologists with a sub-speciality interest in medical retina. RESULTS: Regarding treatment decision for optometrists, the percentage correct value was 75% with the sensitivity being 75.6% (95% CI 70.1-80.3) and the specificity as 75.1% (95% CI 72.1-77.8). No statistically significant difference was found between differing levels of experience. However, there was a significant difference in confidence levels between groups. Potentially sight threatening decisions accounted for 6.4% of the optometrists' decisions, 3.5% were made with a high confidence rating suggesting no discussion with an ophthalmologist was required. CONCLUSIONS: Although the optometrists showed modest agreement with the reference standard in a series of cases that have higher than average complexity, the optometrists showed a similar amount of variability within their treatment decisions compared to the reference standard. The optometrists were therefore not inferior in their performance compared to the ophthalmologists and this can be seen as supporting evidence for their extended role within this clinical area. Experience did not have an effect on 'correct' treatment decisions although there was a statistically significant effect on increasing confidence of treatment decision.

Targeting macrophages and their recruitment in the oral cavity using swellable (+) alpha tocopheryl phosphate nanostructures.

The phosphorylation of (+) alpha tocopherol produces adhesive nanostructures that interact with oral biofilms to restrict their growth. The aim of this work was to understand if these adhesive (+) alpha tocopheryl phosphate (α-TP) nanostructures could also control macrophage responses to the presence of oral bacteria. The (+) α-TP planar bilayer fragments (175 nm ±â€¯21 nm) formed in a Trizma®/ethanol vehicle swelled when exposed to the cell lines (maximum stabilized size = 29 µm). The swelled (+) α-TP aggregates showed selective toxicity towards THP-1 macrophages (LD50 = 304 µM) compared to human gingival fibroblasts (HGF-1 cells; LD50 > 5 mM), and they inhibited heat killed bacteria stimulated MCP-1 production in both macrophages (control 57.3 ±â€¯18.1 pg/mL vs (+) α-TP 6.5 ±â€¯3.2 pg/mL) and HGF-1 cells (control 673.5 ±â€¯133 pg/mL vs (+) α-TP - 463.9 ±â€¯68.9 pg/mL).

Soft, adhesive (+) alpha tocopherol phosphate planar bilayers that control oral biofilm growth through a substantive antimicrobial effect.

'Soft' nanomaterials have the potential to produce substantive antibiofilm effects. The aim of this study was to understand the oral antimicrobial activity of soft nanomaterials generated from alpha-tocopherol (α-T) and alpha-tocopherol phosphate (α-TP). (+) α-TP formed planar bilayer islands (175 ± 21 nm, -14.9 ± 3.5 mV) in a Trizma® buffer, whereas (+) α-T formed spherical liposomes (563 ± 1 nm, -10.5 ± 0.2 mV). The (+) α-TP bilayers displayed superior Streptococcus oralis biofilm growth retardation, a more substantive action, generated a superior adsorption to hydroxyapatite and showed an enhanced inhibition of multi-species bacterial saliva biofilm growth (38 ± 7µm vs 58 ± 18 µm, P ˂ 0.05) compared to (+) α-T. Atomic force microscopy data indicated that the ability of the 'soft' α-TP nanomaterials to transition into planar bilayer structures upon contact with interfaces facilitated their adhesive properties and substantive antimicrobial effects.

Effectiveness of portable electronic and optical magnifiers for near vision activities in low vision: a randomised crossover trial.

PURPOSE: To compare the performance of near vision activities using additional portable electronic vision enhancement systems (p-EVES), to using optical magnifiers alone, by individuals with visual impairment. METHODS: A total of 100 experienced optical aid users were recruited from low vision clinics at Manchester Royal Eye Hospital, Manchester, UK, to a prospective two-arm cross-over randomised controlled trial. Reading, performance of near vision activities, and device usage were evaluated at baseline; and at the end of each study arm (Intervention A: existing optical aids plus p-EVES; Intervention B: optical aids only) which was after 2 and 4 months. RESULTS: A total of 82 participants completed the study. Overall, maximum reading speed for high contrast sentences was not statistically significantly different for optical aids and p-EVES, although the critical print size and threshold print size which could be accessed with p-EVES were statistically significantly smaller (p < 0.001 in both cases). The optical aids were used for a larger number of tasks (p < 0.001), and used more frequently (p < 0.001). However p-EVES were preferred for leisure reading by 70% of participants, and allowed longer duration of reading (p < 0.001). During the study arm when they had a p-EVES device, participants were able to carry out more tasks independently (p < 0.001), and reported less difficulty with a range of near vision activities (p < 0.001). CONCLUSIONS: The study provides evidence that p-EVES devices can play a useful role in supplementing the range of low vision aids used to reduce activity limitation for near vision tasks.

Effectiveness of UK optometric enhanced eye care services: a realist review of the literature.

PURPOSE: UK demographic and legislative changes combined with increasing burdens on National Health Service manpower and budgets have led to extended roles for community optometrists providing locally-commissioned enhanced optometric services (EOS). This realist review's objectives were to develop programme theories that implicitly or explicitly explain quality outcomes for eye care provided by optometrists via EOS and to test these theories by investigating the effectiveness of services for cataract, glaucoma, and primary eye care. METHODS: The review protocol was published on PROSPERO, and RAMESES publication standards were followed. Programme theories were formulated via scoping literature searches and expert consultation. The searching process involved all relevant electronic databases and grey literature, without restrictions on study design. Data synthesis focussed on questioning the integrity of each theory by considering supportive and refuting evidence from the source literature. RESULTS: Good evidence exists for cataract, glaucoma and primary eye care EOS that: with appropriate training, accredited optometrists manage patients commensurate with usual care standards; genuine partnerships can exist between community and hospital providers for cataract and glaucoma EOS; patient satisfaction with all three types of service is high; cost-effectiveness of services is unproven for cataract and primary eye care, while glaucoma EOS cost-effectiveness depends on service type; contextual factors may influence service success. CONCLUSIONS: The EOS reviewed are clinically effective and provide patient satisfaction but limited data is available on cost-effectiveness.

Providing capacity in glaucoma care using trained and accredited optometrists: A qualitative evaluation.

INTRODUCTION: The role of optometrists in glaucoma within primary and secondary care has been well described. Whilst many studies examined safety and clinical effectiveness, there is a paucity of qualitative research evaluating enablers and barriers for optometrists delivering glaucoma care. The aims of this study are to investigate qualitatively, and from a multi-stakeholder perspective whether optometric glaucoma care is accepted as an effective alternative to traditional models and what contextual factors impact upon their success. METHODS: Patients were recruited from clinics at Manchester Royal Eye Hospital and nationally via a Glaucoma UK registrant database. Optometrists, ophthalmologists, and other stakeholders involved in glaucoma services were recruited via direct contact and through an optometry educational event. Interviews and focus groups were recorded and transcribed anonymously, then analysed using the framework method and NVivo 12. RESULTS: Interviews and focus groups were conducted with 38 participants including 14 optometrists and 6 ophthalmologists (from all 4 UK nations), and 15 patients and 3 commissioners/other stakeholders. Themes emerging related to: enablers and drivers; challenges and barriers; training; laser; professional practice; the role of other health professionals; commissioning; COVID-19; and patient experience. CONCLUSION: Success in developing glaucoma services with optometrists and other health professionals is reliant on multi-stakeholder input, investment in technology and training, inter-professional respect and appropriate time and funding to set up and deliver services. The multi-stakeholder perspective affirms there is notable support for developing glaucoma services delivered by optometrists in primary and secondary care, with caveats around training, appropriate case selection and clinical responsibility.

Patient preferences for ocular hypertension monitoring: a discrete choice experiment.

BACKGROUND/AIMS: To elicit the preferences and calculate the willingness to pay (WTP) of patients with ocular hypertension (OHT) for eye monitoring services in the UK. METHODS: Patients with OHT aged at least 18 years recruited from four NHS ophthalmology departments were included in the study. Patients' preferences and WTP for an OHT monitoring service in the National Health Service were elicited using a discrete choice experiment (DCE) within a postal survey based on six attributes: (1) how OHT monitoring is organised, (2) monitoring frequency, (3) travel time from home, (4) use of a risk calculator for conversion to glaucoma, (5) risk of developing glaucoma in the next 10 years and (6) cost of monitoring. We used a sequential mixed-methods approach to design the survey. RESULTS: 360 patients diagnosed with OHT were recruited with a mean age of 69 years. In the DCE, reducing the risk of conversion to glaucoma was the most important factor influencing respondents' choice of monitoring service. Respondents preferred hospital-based monitoring services to community optometrist monitoring, and annual monitoring compared with more frequent (every 6 months) and less frequent (every 18 or 24 months) monitoring. These results can be monetised using WTP. Results of heterogeneity analysis suggest that patients with prior experience in community optometrist monitoring preferred this to hospital-based monitoring. CONCLUSIONS: Although hospital-based monitoring is generally preferred, patients with prior experience in community services have a different opinion, suggesting that patients who are unfamiliar with community optometry services may need additional support to accept monitoring in this setting.

Primary Eyecare Glaucoma Service (PEGS): a mixed methods service evaluation.

PURPOSE: A pilot study to assess the safety and efficacy of a Primary Eyecare Glaucoma Service (PEGS), with low-risk glaucoma patients being reviewed within primary care optometry. METHODS: 98 low-risk glaucoma patients were identified as suitable for monitoring in primary care and reviewed by accredited optometrists in community practice supported by a clinical management plan. Safety was assessed by reviewing concordance of management plans created by primary care optometrists and the secondary care team. Patients' and primary care optometrists' feedback were collated via surveys. Carbon emissions were calculated through comparison of patient travel to primary and secondary care. RESULTS: 93.8% of patients reviewed by primary care met criteria for ongoing monitoring in primary care after initial review with 4.9% of patients being recalled to secondary care due to clinical instability. Safety and efficacy were demonstrated with agreement of management plans between primary and secondary care of 97.8%, kappa =0.88 (95% confidence intervals 0.60-1.00), with no patients being identified as false negatives where recall back to secondary care was required. Overall satisfaction with PEGS was 100% according to a patient survey. Respondents of the primary care optometry survey felt very or somewhat confident in delivering care, with comments suggesting they felt supported by secondary care. Carbon emissions are reduced by approximately two thirds when patients are seen in primary care versus attending the hospital. CONCLUSION: PEGS is a safe and effective service, reducing the burden for secondary care, while carbon emissions are reduced due to shorter travelling distances, demonstrating environmental sustainability.

Risk of Falls and Fractures in Individuals With Cataract, Age-Related Macular Degeneration, or Glaucoma.

Importance: Three leading disease causes of age-related visual loss are cataract, age-related macular degeneration (AMD), and glaucoma. Although all 3 eye diseases have been implicated with falls and fracture risk, evidence is mixed, with the contribution of different eye diseases being uncertain. Objective: To examine whether people with cataract, AMD, or glaucoma have higher risks of falls or fractures than those without. Design, Setting, and Participants: This cohort study was a population-based study in England using routinely collected electronic health records from the Clinical Practice Research Datalink (CPRD) GOLD and Aurum primary care databases with linked hospitalization and mortality records from 2007 to 2020. Participants were people with cataract, AMD, or glaucoma matched to comparators (1:5) by age, sex, and general practice. Data were analyzed from May 2021 to June 2023. Exposures: For each eye disease, we estimated the risk of falls or fractures using separate multivariable Cox proportional hazards regression models. Main Outcomes: Two primary outcomes were incident falls and incident fractures derived from general practice, hospital, and mortality records. Secondary outcomes were incident fractures of specific body sites. Results: A total of 410 476 people with cataract, 75 622 with AMD, and 90 177 with glaucoma were matched (1:5) to 2 034 194 (no cataract), 375 548 (no AMD), and 448 179 (no glaucoma) comparators. The mean (SD) age was 73.8 (11.0) years, 79.4 (9.4) years, and 69.8 (13.1) years for participants with cataract, AMD, or glaucoma, respectively. Compared with comparators, there was an increased risk of falls in those with cataract (adjusted hazard ratio [HR], 1.36; 95% CI, 1.35-1.38), AMD (HR, 1.25; 95% CI, 1.23-1.27), and glaucoma (HR, 1.38; 95% CI, 1.35-1.41). Likewise for fractures, there were increased risks in all eye diseases, with an HR of 1.28 (95% CI, 1.27-1.30) in the cataract cohort, an HR of 1.18 (95% CI, 1.15-1.21) for AMD, and an HR of 1.31 (95% CI, 1.27-1.35) for glaucoma. Site-specific fracture analyses revealed increases in almost all body sites (including hip, spine, forearm, skull or facial bones, pelvis, ribs or sternum, and lower leg fractures) compared with matched comparators. Conclusions and Relevance: The results of this study support recognition that people with 1 or more of these eye diseases are at increased risk of both falls and fractures. They may benefit from improved advice, access, and referrals to falls prevention services.

Advanced Time-Stepping Interpretation of Fly-Scan Continuous Rotation Synchrotron Tomography of Dental Enamel Demineralization.

High-resolution spatial and temporal analysis and 3D visualization of time-dependent processes, such as human dental enamel acid demineralization, often present a challenging task. Overcoming this challenge often requires the development of special methods. Dental caries remains one of the most important oral diseases that involves the demineralization of hard dental tissues as a consequence of acid production by oral bacteria. Enamel has a hierarchically organized architecture that extends down to the nanostructural level and requires high resolution to study its evolution in detail. Enamel demineralization is a dynamic process that is best investigated with the help of in situ experiments. In previous studies, synchrotron tomography was applied to study the 3D enamel structure at certain time points (time-lapse tomography). Here, another distinct approach to time-evolving tomography studies is presented, whereby the sample image is reconstructed as it undergoes continuous rotation over a virtually unlimited angular range. The resulting (single) data set contains the data for multiple (potentially overlapping) intermediate tomograms that can be extracted and analyzed as desired using time-stepping selection of data subsets from the continuous fly-scan recording. One of the advantages of this approach is that it reduces the amount of time required to collect an equivalent number of single tomograms. Another advantage is that the nominal time step between successive reconstructions can be significantly reduced. We applied this approach to the study of acidic enamel demineralization and observed the progression of demineralization over time steps significantly smaller than the total acquisition time of a single tomogram, with a voxel size smaller than 0.5 µm. It is expected that the approach presented in this paper can be useful for high-resolution studies of other dynamic processes and for assessing small structural modifications in evolving hierarchical materials.

The DIAD Approach to Correlative Synchrotron X-ray Imaging and Diffraction Analysis of Human Enamel.

The Dual Imaging and Diffraction (DIAD) beamline at Diamond Light Source (Didcot, U.K.) implements a correlative approach to the dynamic study of materials based on concurrent analysis of identical sample locations using complementary X-ray modalities to reveal structural detail at various length scales. Namely, the underlying beamline principle and its practical implementation allow the collocation of chosen regions within the sample and their interrogation using real-space imaging (radiography and tomography) and reciprocal space scattering (diffraction). The switching between the two principal modes is made smooth and rapid by design, so that the data collected is interlaced to obtain near-simultaneous multimodal characterization. Different specific photon energies are used for each mode, and the interlacing of acquisition steps allows conducting static and dynamic experiments. Building on the demonstrated realization of this state-of-the-art approach requires further refining of the experimental practice, namely, the methods for gauge volume collocation under different modes of beam-sample interaction. To address this challenge, experiments were conducted at DIAD devoted to the study of human dental enamel, a hierarchical structure composed of hydroxyapatite mineral nanocrystals, as a static sample previously affected by dental caries (tooth decay) as well as under dynamic conditions simulating the process of acid demineralization. Collocation and correlation were achieved between WAXS (wide-angle X-ray scattering), 2D (radiographic), and 3D (tomographic) imaging. While X-ray imaging in 2D or 3D modes reveals real-space details of the sample microstructure, X-ray scattering data for each gauge volume provided statistical nanoscale and ultrastructural polycrystal reciprocal-space information such as phase and preferred orientation (texture). Careful registration of the gauge volume positions recorded during the scans allowed direct covisualization of the data from two modalities. Diffraction gauge volumes were identified and visualized within the tomographic data sets, revealing the underlying local information to support the interpretation of the diffraction patterns. The present implementation of the 4D microscopy paradigm allowed following the progression of demineralization and its correlation with time-dependent WAXS pattern evolution in an approach that is transferable to other material systems.

Synchrotron X-ray Studies of the Structural and Functional Hierarchies in Mineralised Human Dental Enamel: A State-of-the-Art Review.

Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical-chemical-structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.

Time-Lapse In Situ 3D Imaging Analysis of Human Enamel Demineralisation Using X-ray Synchrotron Tomography.

Caries is a chronic disease that causes the alteration of the structure of dental tissues by acid dissolution (in enamel, dentine and cementum) and proteolytic degradation (dentine and cementum) and generates an important cost of care. There is a need to visualise and characterise the acid dissolution process on enamel due to its hierarchical structure leading to complex structural modifications. The process starts at the enamel surface and progresses into depth, which necessitates the study of the internal enamel structure. Artificial demineralisation is usually employed to simulate the process experimentally. In the present study, the demineralisation of human enamel was studied using surface analysis carried out with atomic force microscopy as well as 3D internal analysis using synchrotron X-ray tomography during acid exposure with repeated scans to generate a time-lapse visualisation sequence. Two-dimensional analysis from projections and virtual slices and 3D analysis of the enamel mass provided details of tissue changes at the level of the rods and inter-rod substance. In addition to the visualisation of structural modifications, the rate of dissolution was determined, which demonstrated the feasibility and usefulness of these techniques. The temporal analysis of enamel demineralisation is not limited to dissolution and can be applied to other experimental conditions for the analysis of treated enamel or remineralisation.